A Mississippi River lock and dam north of St. Louis has reopened after a towboat spilled about 50 gallons of diesel while passing through the lock.

The Army Corps of Engineers said in a release that the lock and dam were closed Wednesday after the spill and reopened later Wednesday evening. The spill occurred at Lock and Dam 25, which is located about 45 miles north of St. Louis.

The Corps of Engineers says crews have completed cleanup operations at the site, and that the cause of the spill is under investigation.